Lubricant separating system for refrigerating machines



Jan. 12 1954 w. ss poosou 2,665,557

LUBRICANT SERARATING SYSTEM FOR REFRIGERATING' MACHINES Filed Feb. 5, 1951 2 Sheets-Sheet l Figl.

Fig.2;

Invrflaor: Wagne E. Dodson His Atto*'neg- Jan. 12, 1954 w. 2. DODSON 2,665,557

LUBRICANT SEPARATING SYSTEM FOR REFRIGERAT-ING MACHINES Filed Feb. 5, 1951 2 Shets-Sh'ee'i 2 Inventor: Wagne E. Dodson,

His Abbot-neg.

Patented Jan. 12, 1954 ice LUBRICANT SEPARATING SYSTEM FOR REFRIGERATING MACHINES Wayne E. Dodson, Caldwell, N. J., assignor to General Electric Company, a corporation of New York Application February 3, 1951, Serial No. 209,273

7 Claims.

This invention relates to refrigerating machines and particularly to systems for separating lubricant from the compressed refrigerant and for returning it to the lubricant sump.

In refrigerating systems of the compression type, lubricant for the moving parts of the compressor is entrained unavoidably in the compressed refrigerant. For effective operation of many types of systems it is desirable to separate the lubricant from the compressed refrigerant before it is delivered to the condenser. It has been found that under certain conditions when the refrigerant compressor is idle, refrigerant may be condensed on the high side of the system and thus there is a likelihood that liquid refrigerant will collect in the oil separator and will be returned to the lubricant sump. This is an undesirable condition which may result in objectionable foaming of the oil in the compressor crankcase or sump when the system is again operated. Accordingly it is an object of this invention to provide a refrigerating system including a separator for removing lubricant from the compressed refrigerant and an improved arrangement for minimizing the return of refrigerant to the lubricant sump.

It is another object of this invention to provide an improved oil separating and return system which is particularly suitable for compression type refrigerating machines in which the condenser is remotely located with respect to the compressor.

Further objects and advantages of this invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of this invention a refrigerating machine of the compression type is provided with an oil separator in the discharge line between the compressor and the condenser, and an oil return line is arranged between the oil separator and the compressor lubricant sump. The return line is provided with a suitable device, such as a float valve, to prevent passage of gaseous refrigerant to the lubricant sump. In order to prevent the passage of liquid refrigerant to the oil sump a second control device is provided for preventing the passage of liquid through the oil return line whenever temperature or pressure conditions in the oil separator are such that liquid refrigerant may exist therein; thus no liquid may flow upon actuation of the float valve under conditions such that the lubricant may carry liquid refrigerant.

For a better understanding of this invention, reference may be had to the accompanying drawings in which Fig. 1 represents diagrammatically a compression type refrigerating system including an o ep t n a n me t em odyin this invention; Fig. 2 is an enlarged diagrammatic view of a modified form of oil separator embodying the invention; Fig. 3 is a view similar to Fig. 1 illustrating a further embodiment; and Fig. 4 is a similar figure illustrating a still further embodiment.

Referring now to the drawings, the refrigerating system illustrated in Fig. 1 includes a compressor I 0' driven by an electric motor I l and arranged to deliver compressed refrigerant through an oil separating apparatus I2 to a condenser l3. The condensed refrigerant collects in the receiver l4 and is delivered to an evaporator l5 under control of a thermostatic expansion valve l6 having a feeler bulb ll responsive to the temperature of the vaporized refrigerant returned to the compressor It. The compressor [0 may be of any suitable type and has been illustrated as being a conventional form of reciprocating compressor which includes a crankcase l8 acting as a sump or reservoir for a body of oil or other liquid lubricant (not shown). Small portions of the oil which is necessary for lubrication of the moving parts of the compressor unavoidably become entrained in the compressed refrigerant during the operation of the compressor and it is desirable to remove the greater portion, if not all, of this oil so. that it is not conducted to the condenser and allowed to flow through the remainder of the closed refrigerant circuit. It is for the purpose of eliminating this oil discharged from the compressor that the oil separating apparatus I2 is provided. This apparatus includes a separator [9 which may beof any suitable construction and which provides a chamber at the bottom of which the separated oil collects. In order to return the oil to the crankcase a valve 2b is provided which is arranged to be actuated by a float 2| which admits the oil to a conduit 22 whenever the level rises above a predetermined value. The oil is thereupon discharged to the sump or crankcase l8 because of the difference in pressure between the chamber l9 and the. crankcase. Under certain conditions of opera-- tion there may be a prolonged period when the: compressor is not in operation during which re-- frigerant on the high side of the system between; the compressor and the condenser may be cooled. and liquefied, the liquid refrigerant flowing to the: oil separator chamber [9 and mingling with the,

oil in the bottom of the chamber. This condition is particularly apt to prevail when the com-- pressor and oil separator are located remote from the condenser E 3 and below the condenser. Thus. the long upright portion of the compressor discharge line indicated at 23 may be subject to substantial cooling during the off period of the compressor. 7

Should the float valve be actuated when there is liquid refrigerant in the chamber I 9 this liquid Wi1l .be returned to the crankcase-through the parent that although the float valve 20 effectively prevents the admission of gaseous refrigerant to the line 22, it alone cannot be reliedupon to prevent the passage of refrigerant in liquid form to the compressor case. In order to minimize or prevent the passage of liquid refrigerantthrough the conduit 22 to the crankcase there is provided a thermostatically operated valve 24 arranged in the conduit 22 and controlled in accordance with the superheat of the refrigerant in the chamber l9 so that the valve 24 remains closed whenever the superheat is below a predetermined value. This valve may be a conventional thermostatic expansion valve which is'res'ponsive to both temperature and pressure of the refrigerant, a rise in temperature tending to open the valve and a rise in pressure tending to close the valve. In the arrangement illustrated the'val-ve 24 is connested in the line 232 in a reverse direction so thatit is responsive to the temperature and pres sure on the intake side rather than on the discharge side, as is the case in the normalcontrol, such as that represented by the thermostatic expansion valve 18; The valve 243 includes a temperature responsive feeler bulb 25 secured in heat exchange relationship with the bottomof the oil separator l9 and a pressure equalizer connection 26 in communication with the interior of the separator chamber. Should the float valve 29 be opened when the value of superheat, as determined by the valve2 l, is below a predetermined value, the valve 24 will 09010886. and flow of liquid through the conduit 22' will be prevented; however, when the system again starts and the operation ofthe compressor increasesthe pressure and temperature in the oil separator, the liquid refrigerant therein will be vaporized and the superheat will rise until the valve 24 is opened; whereupon the oil'remaining in the bottom of the chamber IE will flow to the sump in the crankcase after it has been freed'of liquid refrigerant.

In Fig. 2 there is illustrated an oil separator 27 which may be connected in a refrigerating system in'the same manner as the separator 19 in Fig; 1 and which is provided with-a combined float valvea'nd superheat responsive mechanism internally of the separator chamber. The'valve indicated at 28"is actuated by a fioat 2-9, and the 'superhea't responsivemechanism comprises a sealed bellows Bdarranged within the chamber 21 and which is opposed by a spring 31 which may be adjumed' by removing a cap 32 and turn ing a screw 33. Movement of the bellows 3t rocks a lever 34 and on contraction of the bellcws'a lug 35 attached to the upper end'of the lever 34 engages an upstanding arm 36 on the float mecn anism to urge the float downwardly and close the valve 28 at a predetermined value of superheat. It will be apparent that the'belloi'v's 3B is responsive both to the pressure in the oil sepa rator chamber 21 and to the temperature therein. When oil collectsin' the bottom of the'chainber 21 it surrounds theb'ellows 30, and should liquid refrigerant be present the temperature within the chamber will remain low until this refrigerant is vaporized afterstarting of the compressor. Thus thebell'ows '38 controls the valve 28' to prevent the passage of liquid refrigerant through the con-'- duit 22 in essentially the same manneras does the valve 24 in Fig; l.

The systemiillustratedin Fig. 3 is essentially similar to Fig; 1 andsconiiespondingparts have been designated by the same numerals. This system differs from that of Fig. l in that a separate float chamber indicated at 31 is provided between the valve 23 and the separator I9, and located below the separator 59 the valve 20 and lessen 2i bang omitted in this case, and a valve 38 actuated by a float 39 arranged in the chamher 3'? being employed instead. In addition the feeler bulb 25 is located to be responsive to the temperature of the float chamber. In order to provide the necessary pressure connection or equalizer between the chamber 19 and valve 24, the pressure connection 26 of the valve is connected to a duct 49 connecting the chamber 31 and the upper portion of the chamber 19 and containing gaseous refrigerant at the pressure within the chamber iii on the discharge side of the compressor. Pressure is thus equalized between the chambers l8 and 31' to assure proper operation of the float valve and is also available for actuation of the valve 25.

The system illustrated in Fig. 4 is also similar to that of 1 and corresponding parts have been designated by the same numerals. This system differs from that of Fig. 1 in that the neat controlled valve is located in a chamber ll in the conduit between the valve 24 and the crankcase of the compressor, no float valve being provided in the separator 19 and a valve 24a corresponding to valve 23 being located adjacent the separator is. The chamber ll and valve 24a must be located below separator id. The valve 25d differs from the valve 2 in that it is of the internally equalized type, the pressure for actuating the pressure responsive device of the valve being that prevailing in the portion 22a of the conduit 22 connecting the valve to the separator chamber i9. This type of valve is well known in the prior art, it being the same as the valve l6 for controlling the flow of refrigerant to the evaporator l5 except the direction of flow is shown reversed. The arrangement of Fig. 4 is particularly suitable for use when the oil separator is located remote from the compressor l0, and in this case a connection 42 between the chamber d! and the discharge line of the com pressor is provided to equalize the pressures in the discharge line and chamber 4!, thereby permitting actuating of a valve 45 upon operation of a float 5% whenever the liquid in the chamber ll rises above a predetermined value, it being clear that in this case the liquid will be oil only since the passage of liquid refrigerant through the valve 2% is prevented by the superheat control of that valve.

From the foregoing it is readily apparent that a simple and effective arrangement has been provided for insuring the retention of liquid refrigerant in the oil separator of a compression type refrigerating system so that it will be evaporated before oil can be returned to the compressor. Thi arrangement prevents the admission of liquid refrigerant to the crankcase and minimizes foaming.

Various modifications and applications of the invention will become apparent to those skilled in the art and it is not desired that the invention be limited to the specific arrangements illustrated and described, and it is intended by the appended claims to cover all modifications within the spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l; A refrigerating system comprising a compressor and a ondenser and an evaporator connected in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, means including a chamber in said circuitbetween the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, means for minimizing the flow of gas through said conduit to said sump, a valve in said conduit for controlling the flow of liquid therethrough, and means responsive to a predetermined low temperature of the liquid on the inlet side of said valve for preventing the flow of liquid from said chamber through said conduit.

A refrigerating system comprising a compressor and a condenser and an evaporator conheated in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, said condenser being located above and remote from said compressor and said circuit including a conduit of substantial length extending downwardly from said condenser toward said compressor whereby during the off period of said compressor refrigerant may condense in said conduit and flow downwardly therethrough, means including a chamber in said circuit bevveen the discharge side of said compressor and the lower end of said conduit for separating oil from the compressed refrigerant flowing to said condenser and for collecting liquid refrigerant returned through said conduit, a second conduit between said chamber and said sump for returning oil to said sump, means for minimizing the iiow of gas through said second conduit to said sum a valve in said second conduit for controlling the flow of liquid therethrough, and means responsive to a predetermined low temperature of the liquid on the inlet side of said "valve for preventing the flow of liquid from said chamber through said second conduit.

3. A refrigerating system comprising a compressor and a condenser and an evaporator con-, nected in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, means including a chamber in said circuit between the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, means for minimizing the flow of gas through said conduit to said sump, and means responsive to the pressure in said chamber and to the temperature of the liquid near the inlet portion of said conduit for preventing the flow of liquid from said chamber through said conduit whenever the superheat of the liquid is less than a predetermined value at which liquid refrigerant may exist in said chamber.

4. A refrigerating system comprising a compressor and a condenser and an evaporator connected in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, means including a chamber in said circuit between the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, a float actuated valve for returning oil to said compressor whenever a predetermined quantity of oil has been collected by said separating means, and means responsive to the temperature of the collected oil for preventing opening of said float valve whenever the temperature of the oil falls below a predetermined value whereby the return of liquid refrigerant to said sump is prevented.

lubricating oil, means including a chamber in said circuit between the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, a float chamber in said conduit and a float actuated valve therein, and a thermostatic valve in said conduit in series with said float valve and responsive to the pressure of the refrigerant in said chamber andto the temperature of the liquid therein for preventing the flow of liquid through said float valve whenever the superheat in'said chamber falls below a predetermined value.

6. A refrigerating system comprising a compressor and a condenser and an evaporator connected in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, means including a chamber in said circuit between the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, a valve at the outlet of said chamber and a float in said chamber for actuating said valve to release liquid from said chamber whenever the level thereof rises above a predetermined value, and means responsive to the temperature in said chamber for preventing opening of said valve wheneverthe temperature in said chamber falls below a predetermined value.

7. A refrigerating system comprising a compressor and a condenser and an evaporator connected in a closed refrigerant circuit, a sump for said compressor arranged to hold a body of lubricating oil, means including a chamber in said circuit between the discharge side of said compressor and said condenser for separating oil from the compressed refrigerant flowing to said condenser, a conduit between said chamber and said sump for returning oil to said sump, a valve in said conduit for controlling the flow of liquid therethrough, means responsive to a predetermined minimum value of superheat of the refrigerant in said chamber for actuating said valve to prevent the iiow of liquid from said chamber through said conduit, a second chamber in said conduit between said valve and said sump, a float actuated valve in said second chamber for permitting a flow of liquid through said conduit only upon the accumulation of a predetermined amount of liquid in said second chamber, and a duct providing communication between said chambers for equalizing the pressures therein.

WAYNE E. DODSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,726,178 Davenport Aug. 27, 1928 1,758,074 Davenport May 13, 1930 1,922,942 Gay Aug. 15, 1933 2,042,394 Gay May 21, 1936 2,149,358 De H. Miller Mar. 7, 1939 2,223,882 Beline Dec. 3, 1940 

